1. Field of the Invention
The present invention relates generally to a wind energy conversion system and, more particularly, to the design and manufacture of a jet assisted contra-rotating wind turbine system.
2. Prior Art
In recent years, it has become apparent that conventional methods of generating electricity will soon be insufficient to meet the world's ever-growing need for electric power. Several factors, including the pollution which results from the combustion of fossil fuels, the dangers associated with the operation of nuclear reactors, and the limitations inherent in the traditional hydroelectric as well as the more modern solar energy approaches to the generation of electricity, have encouraged the development of alternative sources of electric power, such as the wind turbine generator.
In recent years, wind energy projects have included the installation of large numbers of wind turbine generating systems at locations having favorable wind conditions. Several of these so-called "wind farms" have been located in the state of California. However, during the 1980s, it became apparent that the various wind energy projects using wind turbines to generate electrical energy suffered from a major problem in that the turbines were not receiving the amount of wind energy that was projected based on the initial wind studies that were conducted. Many reasons have been advanced for this shortfall of wind energy. Little can be done about the wind itself, with the exception of understanding the available resource better by using direct measurement and analysis. However, a new rotor blade system according to the present invention, designed to take better advantage of the available wind resource, provides an opportunity for a significant energy increase.
As noted, then, wind turbines are renewable energy devices that are currently useful but not able to optimally extract energy from the wind. According to Albert Betz, a German engineer, pioneer in optimizing wind energy utilization, and author in 1926 of "Wind Energie und Ausnutzung durch Windmuehlen", an ideal rotor disk can deliver to a selected task 59% of the total wind energy generated. For example, an ideal rotor disk is expected to yield 797 watts per square meter at 13 m/sec of wind speed. In contrast, a practical wind turbine, according to Paul Gipe, a more recent well known promoter of wind energy technology in the United States, author of many books on the subject, his most recent contribution being "Wind Energy Comes of Age", John Wiley & Sons, Inc., New York, 1995, can only deliver less than 20% of the available power which is about 100 to 250 watts/m.sup.2. Even the most acclaimed Bergey's BWC EXCEL wind turbine yields only 260 watts/m.sup.2. Michael Bergey is a small wind turbine manufacturer in the United States whose BWC EXCEL model is generally considered to be the most efficient wind turbine machine in the United States. The reason for such a significantly low energy conversion efficiency may be attributed to the downstream velocity (V.sub.2) being greater than one half of the upstream velocity (V.sub.1). Thus, a wind turbine comprising of a single rotor system cannot possibly extract the amount of power suggested by Betz. Consequently, more than 60% of the usable energy is swept away in the downstream wind. Another drawback of a single rotor system is that it experiences a large power loss resulting from drag associated with high tip speed of large diameter rotor. Then too, single rotor renewable energy devices are limited in their use since a high torque is necessary to self start the system and therefore can be installed only in regions with consistently high wind speeds.
A small number of patents are typical of the known prior art attempting to improve on earlier efforts to harness wind energy. For example, U.S. Pat. No. 5,456,579 to Olson discloses a wind turbine blade with a governor to maintain optimum rotational speed. The governor positions an aileron for varying wind speed and includes a lead weight positioned at the wing tip and connected to a mechanism that deploys the aileron to achieve the maximum lift to drag ratio at all wind speeds. U.S. Pat. No. 5,419,683 to Peace discloses a method of installing a plurality of wind turbines on chimneys, towers or the like. Two rotors having their horizontal axes are mounted back to back on a ring that turns about the chimney. The primary concept of this invention is to utilize existing structures to mount a plurality of wind turbines and to eliminate the need for wind farms. U.S. Pat. No. 4,976,587 to Johnston et al. discloses a method for manufacturing composite blades having highly improved aerodynamic efficiency. The blades employ the NASA airfoil section LS(1)-04XX having 29 per cent thickness at 3/10 radius and 18 per cent at the blade tip. The airfoil section comprises two spars which terminate into a circular section at the hub. U.S. Pat. No. 4,648,801 to Wilson discloses a method of compressing air by means of a wind turbine. The air is drawn from the low energy region of the downwind stream. The compressed air is connected to the intake of a prime mover (such as a diesel engine, a gasoline engine, or a gas turbine) to boost its output power and drives an alternator.
It was with knowledge of the foregoing state of the technology that the present invention has been conceived and is now reduced to practice.